What percent of the time do you use tenkara compared to "regular" rod and reel?

I can't give you a % of use.
It depends on where I'm fishing. It is awesome for pocket water, you don't have to worry about your back cast or conflicting currents. For those you can just reach over them and drift your fly through them. I fish both drys and s/h's with it. When using s/h's you can work the fly like western fisher folks could never imagine.
I fished Cattaloochee last year and caught at least 30 in the are from the check in station to the second bridge. All on drys and fishing up stream.